Date of Award

12-2018

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Environmental Engineering and Earth Sciences

Committee Member

Dr. Tanju Karanfil, Committee Chair

Committee Member

Dr. Cindy Lee

Committee Member

Dr. David Ladner

Abstract

The main goal of this work is to investigate the formation and speciation of disinfection by-products (DBPs) in treated wastewater samples following chlorine oxidation. Disinfection is an essential process in water and wastewater treatment to remove pathogens. However, it was discovered that the use of chlorine for disinfection also results in some toxic chemicals known as disinfection by-products. Since the 1970s, more than 600 DBPs have been discovered, and the control of DBPs has become one of the main issues for drinking water regulations, treatment operations and researchers. Almost two billion people living in different regions or countries are going to face absolute water scarcity and two-thirds of the world population could be under water stress condition by 2025. Therefore, it is important to diversify water sources with alternative sources to reduce the risk of water paucity. As a result, wastewater-impacted water sources have been increasingly considered in water treatment. Chlorination of water containing high concentrations of bromide and nitrogen favor the formation of regulated and unregulated DBPs. The effluent organic matter (EfOM) of treated wastewater includes more nitrogen-containing compounds than natural organic matter (NOM) (e.g N/C mass ratios of EfOM and NOM are ~ 0.20 and 0.01-0.06, respectively). Additionally, the concentrations of bromide and iodide are higher in wastewater effluents compared to surface waters. Formation of iodinated and brominated DBPs which are more toxic than their chlorinated analogues is favored. Although the literature is rich with studies focusing on DBPs formation from NOM and in fresh waters, there is still limited information about DBPs` formation and speciation from EfOM in treated wastewater effluents. For future indirect (IPR) or direct potable reuse (DPR) applications, it is essential to increase our knowledge related to DBPs formation in effluent-impacted waters. The result of this work showed that initial bromide concentration was the most important factor affecting formation and speciation of DBPs among the factors tested, which included bromide concentration, EfOM type, pH and chlorine dose. Higher bromide concentration increased both total trihalomethanes (TTHM) and total haloacetonitriles (THAN) formation. However, total haloacetic-aid (HAA) formation did not increase. Additionally, THM formation was favored in alkaline condition, but HAN formation decreased with the higher pH value. Moreover, HAA formation was favored in neutral condition. Effect of chlorine dose was not as effective as the bromide concentration and pH on DBPs formation. Higher chlorine dose slightly increased both THMs and HAAs, but THAN formation decreased. Lastly, between different samples DBPs formation and speciation was not considerably different. However, some differences were observed such as chlorine dose affected formation of THAN at different rates for samples WWTP 2 and WWTP 5.

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